From: Hans Verkuil <hverkuil@xs4all.nl>
To: Helmut Grohne <helmut.grohne@intenta.de>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
"tfiga@chromium.org" <tfiga@chromium.org>,
"bingbu.cao@intel.com" <bingbu.cao@intel.com>,
"jian.xu.zheng@intel.com" <jian.xu.zheng@intel.com>,
"rajmohan.mani@intel.com" <rajmohan.mani@intel.com>,
"tian.shu.qiu@intel.com" <tian.shu.qiu@intel.com>,
"ricardo.ribalda@gmail.com" <ricardo.ribalda@gmail.com>,
"grundler@chromium.org" <grundler@chromium.org>,
"ping-chung.chen@intel.com" <ping-chung.chen@intel.com>,
"andy.yeh@intel.com" <andy.yeh@intel.com>,
"jim.lai@intel.com" <jim.lai@intel.com>,
"laurent.pinchart@ideasonboard.com"
<laurent.pinchart@ideasonboard.com>,
"snawrocki@kernel.org" <snawrocki@kernel.org>
Subject: Re: [PATCH 2/5] v4l: controls: Add support for exponential bases, prefixes and units
Date: Mon, 1 Oct 2018 11:48:53 +0200 [thread overview]
Message-ID: <62eb24aa-2221-c156-16d3-3e4bd5d32841@xs4all.nl> (raw)
In-Reply-To: <20181001092758.ionkxntgduvq2puv@laureti-dev>
On 10/01/2018 11:27 AM, Helmut Grohne wrote:
> On Fri, Sep 28, 2018 at 04:00:17PM +0200, Hans Verkuil wrote:
>> On 09/25/2018 12:14 PM, Sakari Ailus wrote:
>>> +/* V4L2 control unit prefixes */
>>> +#define V4L2_CTRL_PREFIX_NANO -9
>>> +#define V4L2_CTRL_PREFIX_MICRO -6
>>> +#define V4L2_CTRL_PREFIX_MILLI -3
>>> +#define V4L2_CTRL_PREFIX_1 0
>>
>> I would prefer PREFIX_NONE, since there is no prefix in this case.
>>
>> I assume this prefix is only valid if the unit is not UNDEFINED and not
>> NONE?
>
> Why should it? The prefix is concerned with rescaling a value prior to
> presenting it to a user. Even a unitless quantity or a value of
> undefined unit can be reasonably scaled. Displaying a unit and scaling
> look like orthogonal concepts to me.
What's the point? If I have a unit-less control with values 1-1000, then
what would a prefix 'milli' tell me as a user? Why would 0.001-1 be better
compared to 1-1000?
Without a unit it is just an integer range and scaling is meaningless.
>
>> Is 'base' also dependent on a valid unit? (it doesn't appear to be)
>
> I'd argue it should not depend on a valid unit like the prefix.
I think I agree with that, although I am dubious about the value of the
base field as I commented on elsewhere.
Regards,
Hans
next prev parent reply other threads:[~2018-10-01 16:25 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-25 10:14 [PATCH 0/5] Add units to controls Sakari Ailus
2018-09-25 10:14 ` [PATCH 1/5] videodev2.h: Use 8 hexadecimals (32 bits) for control flags Sakari Ailus
2018-09-28 13:16 ` Laurent Pinchart
2018-09-28 13:48 ` Hans Verkuil
2018-09-25 10:14 ` [PATCH 2/5] v4l: controls: Add support for exponential bases, prefixes and units Sakari Ailus
2018-09-28 14:00 ` Hans Verkuil
2018-10-01 9:27 ` Helmut Grohne
2018-10-01 9:48 ` Hans Verkuil [this message]
2018-11-14 9:09 ` Tomasz Figa
2018-10-14 6:14 ` Pavel Machek
2018-09-25 10:14 ` [PATCH 3/5] Documentation: media: Document control exponential bases, units, prefixes Sakari Ailus
2018-09-25 10:39 ` Helmut Grohne
2018-09-25 10:51 ` Sakari Ailus
2018-09-28 14:20 ` Hans Verkuil
2018-09-25 10:14 ` [PATCH 4/5] v4l: controls: QUERY_EXT_CTRL support for base, prefix and unit Sakari Ailus
2018-09-26 22:40 ` kbuild test robot
2018-09-28 14:23 ` Hans Verkuil
2018-09-25 10:14 ` [PATCH 5/5] smiapp: Set control units Sakari Ailus
2018-09-28 14:28 ` Hans Verkuil
2018-09-25 11:48 ` [PATCH 0/5] Add units to controls Helmut Grohne
2018-09-25 12:30 ` Sakari Ailus
2018-09-26 10:24 ` Helmut Grohne
2018-09-28 13:25 ` Laurent Pinchart
2018-09-28 14:36 ` Hans Verkuil
2018-10-03 9:15 ` Tomasz Figa
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